the fbi says the suspect paul kevin curtis sent three letters all of which preliminarily tested positive for the definitely poison ricin, produced from castor beans. one to president obama, another to mississippi republican senator roger wicker, and a third, local authorities said, to a mississippi justice official. >> there are great consistencies between the content, the letter itself, the way the letter was written, the postmark of the letter. >> reporter: the fbi says the letters to the president and senator were postmarked memphis, tennessee, ten days ago with identical language including the phrase, to see a wrong and not expose it is to become a silent partner to its continuance. signed iak.c., i am k.c., and i approve this message. those were never delivered. intercepted by a precaution put in place after the anthrax attacks that killed five people shortly after 9/11. and federal officials say more tests are needed, natalie, to determine if, in fact, that substance was ricin, and if so, how strong. the fib also says these see no connection between this ricin-tainted scare and wha